Intermediate frequency transformer with toroidal coils



Sept. 30, 1958 A. M. BOOTHE 2,854,642

INTERMEDIATE FREQUENCY TRANSFORMER WITH TOROIDAL COILS Filed 001.- 25, 1955 INVENTOR.

ALONZO M. BOOTHE, BY mm m QM M4IZ.A7M.

ATTORNEYS.

United States Patent F INTERMEDIATE FREQUENCY TRANSFORNIER WITH TOROIDAL COILS Alonzo M. Boothe, Cincinnati, Ohio, assignor to Aneo Manufacturing Corporation, Cincinnati, Ohio, :1 corporation of Delaware Application October 25, 1955, Serial No. 542,746

4 Claims. (Cl. 333-78) The present invention relates generally to intermediate frequency (I. F.) signal transformers, and specifically provides a miniature I. F. transformer of particularly stable gain and uniform band width characteristics.

A- specific object of the invention is to provide a compact I. F. transformer which satisfies the following electrical requirements:

Q of each inductance: 155 at 6.9 megacycles per second Band width characteristics of a four-stage amplifier employing five of these transformers: 54 kilocycles (kc.) at the 6 db points and 155 kc. at the 60 db points Over-all gain of such an amplifier: 120 db Another object of the invention is to provide an I. F. transformer structure as a stacked arrangement of coils and capacitors, with means for adjusting the coupling arranged in such a way as readily to utilize the available space and provide means of doing same after sealing of the assembly.

For a better understanding of the invention, together with other and further objects, advantages, and capabilities thereof, reference is made to the following description of the accompanying drawings.

In the drawings:

Fig. 1 is a perspective view showing my improved transformer structure with the shielding can in place;

Fig. 2 is a front elevational sectional view taken along the section line 2-2 of Fig. 3 and looking in the direction of the arrows;

Fig. 3 is a side elevational sectional view taken along the section line 33 of Fig. 2;

Figs. 4 and 5 are plan views, as taken in section, respectively, along the section lines 4-4 and 5--5 of Fig. 2;

Fig. 6 is an elevational sectional view showing the details of one of the terminal lugs and associated structure, as taken along the section line 66 of Fig. 2; and

Fig. 7 is a circuit diagram of the entire transformer unit in accordance with the invention.

This transformer is of particular utility in the localizer receiver of a localizer path unit. In order to assure a high Q and a concentrated electro-magnetic field, the invention utilizes miniature iron core toroidal coils 10 and 11, best shown in Figs. 2 and 5. The concentrated field is required in order to minimize the loading effects and reduction of Q caused by the placement of the coils in close proximity to the copper shield cover or can 12. As indicated in Fig. 7, the coils 10 and 11, constituting the primary and secondary of the I. F. transformer, are individually tuned by their respective groups of capacitors 13--14 for the primary and 15-16 for the secondary. The coils and capacitors are connected in the customary electrical fashion to constitute a double-tuned circuit meeting the requirements mentioned above. The primary connections are brought out to terminal lugs 21 and 22 and the secondary connections are brought out to terminal lugs 23 and 24.

The mechanical framework of the transformer is pro- 2,854,642 Patented Sept. 30, 1958 vided by a generally rectangular copper base 25, which is flanged to secure can 12 in assembly. Rigidly mounted on the base near the corners thereof are four conductive metallic terminal posts 31, 32, 33, and 34. Each of these posts is rigidly mounted on the base 25 by means such as that detailed in Fig. 6 and hereinafter described.

To complete the structural supporting arrangements for the coils and capacitors, I provide, successively spaced from the base 25 and from each other, a plurality of phenolic boards 26, 27, and 28, each generally rectangular in shape and provided with suitable eyelets, such as that indicated at 29, so that the boards can be slipped onto the terminal posts and then suitablysoldered into secure relationship thereto.

The trimmer capacitors 16 and 14 are secured to the bottom of board 26 and mounted with their conductive leads on top of the board and their adjusting screws 35 and 36 in registry with access openings provided by sleeves 37 and 38, the latter being suitably secured to base 25 and in turn provided with sealing nuts 39 and 40, the removal of which permits ready adjustment of the trimming capacitors 16 and 14. In the space between boards 26 and 27, the leads of the trimmer capacitors are suitably brought out and soldered to the appropriate terminal posts, as shown in Fig. 4.

The iron cores and coils 10 and 11 are secured in place between boards 27 and 28 by suitable forms arranged to form dowel joints such as 41, 19 with the boards.

Fixed capacitors 13 and 15 are mounted above board 28 and secured to the terminal posts in the manner illustrated in Fig. 2.

It will be seen, therefore, that the invention provides a compact arrangement of coils and capacitors. For the purpose of adjusting the coupling between the coils 10 and 11 without increasing the space requirements, I provide a powdered iron slug 42, positioned adjacent the facing edges of the coils 10 and 11, with its longitudinal axis parallel to the central axes of the two coils. The slug 42 projects through complementary apertures in boards 26 and 27, and its position is adjusted by a brass adjusting screw 43 to which it is secured, the screw in turn engaging a complementary internally threaded fitting 44 on base 25. The board 28 functions as a limit stop to terminate displacement of core 42.

The coupling between the coils is made aiding in character when an iron core 42 is used. Optionally a brass core with bucking coupling may be employed.

I have found that by arranging the windings in a nonsymmetrical or offset fashion, as shown by the reference numeral 45 in Fig. 5, the degree of coupling variation for any given displacement of the core 42 may be increased.

The leads of the coil formsare rigidly secured in place by passing them through apertures in the iron cores, as illustrated by the reference numerals 47 and 48 in Fig. 2.

The details ofthe arrangement of terminal lug 24, which is typical, are illustrated in Fig. 6. Positioned in abutment with the base 25 is a plastic insulator 49 internally bored to receive an elongated eyelet 50 and countersunk to receive the insert portion of grommet 51. Adjacent the grommet is a washer 23. The crimped ends of the eyelets 50 secure in position the terminal lug 24, the insulator 49, the grommet 51, and the washer 23. Post 34 has a reduced portion passing through washer 53 and and eyelet 50 and soldered to the eyelet at 52.

In one practical embodiment of the invention, designed for operation in a localizer receiver at 6.9 megacycles, the fixed capacitors employed have values of 270 micromicrofarads each, and each of the trimmer capacitors is adjustable between 20 and 60 micromicrofarads.

I desire in the appended claims to cover a reasonable range of equivalents.

1. A transformer comprising: a first magnetic toroidal core; a second magnetic toroidal core, said first and second magnetic toroidal cores being fixedly disposed with their central axes parallel; a metallic slug couplingadjusting means mounted in parallel with said axes and spaced therefrom at a point equidistant fromsaid axes; a primary winding wound on a portion of said firstmagnetic toroidal coil and a secondary winding wound on a portion of said second magnetic toroidal core, said windings being disposed on said cores so that the ends of said primary winding and the ends of said secondary winding are spaced unequal distances from said metallic slug coupling-adjusting means;=and means for moving said metallic. slug coupling-adjusting means parallel to said axesfor changing the magnetic coupling between said primary andsaid secondary windings.

2. In an intermediate frequency transformer ;a housing comprising a conductive metallic can and a base, four upwardly projecting terminal posts mounted at the corners of said base and insulated therefrom, three spaced insulating boards securedto said posts, wafer-shaped primary and secondary trimmer capacitors secured in the compartment between the base and the first board, said capacitors having leads brought out and secured to :said postsin the compartment between said first board and the second board, toroidal-shaped iron-core primary and secondary coils secured in the compartment between said second board and the third board, primary and secondary fixed capacitors secured to said third board, a couplingadjusting slug slidably mounted in such a manner that its axis is parallel to and offset from the central :axes of said coils, said slug projecting through apertures in said first and second boards and utliizing said thirdboard as a limit stop, a screw-threaded extension of 'said slug adjustably projecting through said base, and sleeves-in said base with removable seals for permitting adjustment .of said trimmers, said coils and condensers being connected to said posts to provide double-tuned circuits.

3. In an intermediate frequency transformer the combination in accordance with claim 2 in which the coils are so wound that the slug is equidistant from the centers of the cores of said coils but not equidistant from the ends of said coils.

4. A transformer comprising: a first magnetic toroidal core; a second magnetic toroidal core, said first and second magnetic toroidal cores being fixedly disposed with their central axes parallel; a metallic slug coupling-adjusting means mounted in parallel with said axes and spaced therefrom at a point in proximity to both said first and second magnetic toroidal cores; a primary winding Wound on a portion of said first magnetic toroidal coil and a secondary winding wound on a portion of said second magnetic toroidal core, said windings being disposed on .said cores so thatthe ends of said primary winding and the ends of said secondary winding are spaced unequal distances from said metallic slug coupling-adjusting means; and means for moving said metallic slug coupling-adjusting means parallel to said axes for changing the magnetic coupling between said primary and said secondary windings.

References-'Citedin the file of this patent UNITED STATES PATENTS 2,206,250 Fill July 2, 1940 2,438,770 Tillman Mar. 30, 1948 2,451,444 Norde Oct. 12, .1948

2,732,529 Ried et a1. Jan. .24, .1956

FOREIGN PATENTS 148,968 Australia Nov. 11, 1952 

